FAA Probes In-Flight Close Calls During Power Outage / Circuit board blamed for lack of radio contact

Manny Fernandez, Chronicle Staff Writer

Published
4:00 am PDT, Friday, August 11, 1995

Federal aviation officials are investigating at least three reports of aircraft flying dangerously close to each other above Northern California during a 65-minute power failure at Fremont's air traffic control center early Wednesday.

The communications breakdown, linked yesterday to a faulty circuit board in a 21-year-old power system, shut off radio and radar communication between the control center and nearly 70 airplanes, leaving the craft without guidance usually received from controllers.

One of the reports involved a United Airlines 757 en route to San Francisco International Airport that came within 1 1/2 miles of a Seattle-bound Alaskan Airlines MD80, said Monte Belger, FAA associate administrator for air traffic services. Aircraft are usually required to keep a distance of at least five miles.

As the two planes passed close to each other over Stockton about 7:30 a.m., on- board alarms warned the pilots that they were in each other's way and instructed the United flight to descend rapidly, said FAA spokesman Hank Verbais.

"Most passengers probably didn't know (the other plane) was there," he said.

Details on the other reports of close calls were not available, Belger said. But air traffic controllers told the Associated Press yesterday that one airliner was 100 to 200 miles off course and in danger of flying into another plane in its path.

According to Belger, none of the incidents was life-threatening and the planes were never in danger.

FAA technicians and engineers continued to search for clues yesterday to explain the power failure that occurred at 7:13 a.m. and lasted until 8:18 a.m. A possible shortage in the center's circuit board is being blamed, Belger said, but investigators do not have all the answers.

"In essence, (the circuit board) burned," Belger said. "It was a circuit board problem with the old system. What caused it, we don't know."

Fremont's three power units were installed in 1974.

The control center, which coordinates traffic in the world's busiest airspace, lost power as maintenance crews took one of three power units off-line for routine modification. The two other units failed for unknown reasons, along with the center's backup system, an engine generator that is supposed to turn on automatically during an outage, Belger said.

He said it is unclear whether the maintenance work caused the outage.

A team of experts and senior FAA officials are focusing their investigation on what caused the shortage and why the backup system failed, Belger said. The search for answers, he added, could take a week or two.

"I hope it won't take that long," he said. "(But) all of the pieces aren't together yet."

Wednesday's power outage occurred a week after the FAA announced plans to replace 25-year-old equipment at five control centers. In the past four months, computers have failed 20 times at control centers in Chicago, Washington, D.C., Dallas- Fort Worth, Cleveland and New York.

But FAA officials are quick to point out that there is no correlation between those equipment defects and Wednesday's outage.

"None of the failures has any consistency," said FAA spokeswoman Carol Long. "It's aging equipment, and it's an issue that the FAA is working on and is aware of."